1. Field of the Invention
The present invention relates to an image forming process for use in electrophotographic copy machines and printers which employ monocomponent and bicomponent developers.
2. Description of the Prior Art
To obtain an image from an electrophotographic copy machine or printer, an electrostatic latent image must first be formed on the surface of a photosensitive member, i.e. an image bearing member. Next, the surface of the photosensitive member having the electrostatic latent image formed thereon is developed with a developer and the obtained toner image is transferred to paper or other media.
The developer used in electrophotographic copy machines and the like is mainly bicomponent developer comprising an insulated non-magnetic toner and magnetic carrier, a monocomponent developer comprising a non-magnetic toner. or a monocomponent developer comprising an insulated magnetic toner.
These types of toner are usually made from thermoplastic resin, coloring agent, and charge regulating agent. In the case of magnetic toner, magnetic particles are incorporated with the aforesaid components.
In recent years in this type of electrophotography, extra small toner was studied as a means of achieving high accuracy images. However, the aforesaid extra small toner has poor flow characteristics, and the photosensitive member is inadequately cleaned following the developing process. Cleaning consists of removing the toner that has not been transferred to the copy paper and which remains adhering to the surface of the photosensitive member by means of a rubber blade. When said cleaning is inadequate, sharp images cannot be formed in subsequent cycles.
Making the toner shape spherical was also studied as a means for stabilizing the amount of charge and improving the flow characteristics, but the spherical particles were also caused the disadvantage of greatly worsening cleaning conditions.
Japanese Laid-Open Patent Application No. 59-102252 discloses the use of a toner which incorporates both spherical toner particles and more uniformly small diameter, irregularly shaped toner particles to improve the unsatisfactory cleaning characteristics caused by making the previously mentioned spherical toner and smaller toner.
Although excellent flow characteristics, very sharp latent image formability and the like are properties of spherical toner, these characteristics were not obtained when a toner mixture incorporating both spherical and irregularly shaped toner was used for developing.